The expression of pluripotency genes regulates properties of cancer stem cells in MCF-7 breast cancer model.

Abstract

e23018 Background: More than 1.6 million cases of breast cancer (BC) are diagnosed annually worldwide. Despite advances in diagnoses and treatment, BC remains the third leading cause of death in women. Metastases and chemotherapy resistance are the main factors contributing to BC mortality. The ability of tumor cells to overcome the drug-induced growth inhibition is now linked to a unique population of cancer initiating tumor cells, often referred as cancer stem cells (CSC). CSC represent a small fraction of tumor cells, therefore, currently used isolation protocols have a low yield and are poorly reproducible, hampering research on the role of these cells in cancer chemoresistance. We propose a novel approach to generate large quantities of CSC-like cells by genetic reprogramming of non-stem cancer cells. Methods: We postulate that CSC-enriched cell line can be developed in vitro by upregulating of proteins controlling cancer cell pluripotency including Oct4, Sox2, NANOG, KLF4 and c-Myc. Increased transcriptional and translational activity of these genes in MCF-7 cells was demonstrated by real time-PCR and Western blot. Proliferation and migration of cells overexpressing Oct4, Sox2, NANOG, KLF4 and c-Myc were analyzed as well. Also, changes in CSC population counts and their sensitivity to chemotherapy were investigated using sphere formation assay. Results: We found that cell proliferation rate was correlated with the expression level of c-Myc and Oct4. Increased CSC counts were found in cells with overexpressed Oct4 (62.7%), KLF4 (97%) and NANOG (121.3%) proteins as compared to the parental cells. Overexpression of SOX2, NANOG and KLF4 significantly increased CSC resistance to docetaxel (83,3±6,8; 93,3±4,5 and 80,3±5,0 spheres respectively) when compared to the original cells (48,3±3,0 spheres). Conclusions: We conclude that overexpression of pluripotency proteins Oct4, Sox2, NANOG, KLF4 and c-Myc changes the CSC counts and proliferation capacity of BC cells. Acknowledgements: The study was funded by RFBR, according to the research project No. 16-34-60210 mol_а_dk, and by Russian Government Program of Competitive Growth of Kazan Federal University.